GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: GadgetX on February 14, 2015, 02:13:03 PM
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I have been experimenting with mods on a 1720T. Would like a 20 -25 shot FPE >15 tune somehow.
Members here sent me a few mod parts and I thank them very much. I was able to shot a max power 10 shot string average of 887 fps with a 10.65 gr pellet. Max power was 927 fps (20.33 fpe), but as most guessed it went down from there.
Mods are .110 port, mod valve stem and with spring 1.5" x .30 x.042.
I have tested it many times with original spring (0 striker, 7.5 spring) which gave the highest shot count (count was 25-30), Stiffer spring which gave the highest FPE. Varied the port from .080, .097, .110. Decrease in shot string was not significant. When I added the stiffer spring the shot count was in the mid-low teens.
May look for a spring 1.75" x .30 x .038. For some reason just estimating, this seems like it would be the sweet spot.
Will post result strings next week when I get home from travel.
Again thanks to all members of this fantastic forum.
M
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Your goal is definitely achievable with the oring buffer. Leave that spring, and do a complete shot string at the initial settings I sent you. Start a little high at 3100psi.
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Here is were I am now.
10.65 gr Barracuda match, stiffer spring, modified valve stem & .110 port. 3000 - 2250 psi fill. Striker at .25, spring at 6.5. FPE 14.98 - 17.02. 26 shots.
I would not mind if the FPS was flatter around 820s.
M
795.8
802.5
814.4
818.9
824.7
835.6
836.6
845.0
843.8
848.1
847.6
846.4
848.3
846.6
843.4
error
837.8
835.9
832.6
826.9
818.7
812.5
808.6
806.1
799.4
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If you cut the first two and last three, it is not far out. Take a turn off the preload and see where you are at. Then very, very, small adjustments to throw.
PS: You are getting better flow with that valve stem.
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Here is were I am now.
10.65 gr Barracuda match, stiffer spring, modified valve stem & .110 port. 3000 - 2250 psi fill. Striker at .25, spring at 6.5. FPE 14.98 - 17.02. 26 shots.
I would not mind if the FPS was flatter around 820s.
M
795.8
802.5
814.4
818.9
824.7
835.6
836.6
845.0
843.8
848.1
847.6
846.4
848.3
846.6
843.4
error
837.8
835.9
832.6
826.9
818.7
812.5
808.6
806.1
799.4
Did you put the O-rings in? I think I'm at about .25-.5 on striker and like 4 on the spring. I start and end right at 800 with a peak of 832 for 23 shots, with 10.3 AA
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I will get back later next week. Off to Mardi Gras this week.
Thanks for the tips I will try next weekend.
M
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Decided to get my 1720 out and run a string. Pumped it to just past the 3K line on gauge. Here are the #'s (I bumped up my external spring adjuster about 1/8 turn) Pellet - 10.3 Air Arms
801.7
808.9
820
822.6
826.8
833.5
837.1
838.9
838.9
841.2
846.9
843.5
840.9
843.4
841.6
839.9
841.7
835.1
835.1
825.7
829.3
821.3
815.3
800.1
If we throw out the 1st and last shot I got 22 shots under 4.4% spread (throw out the 1st two and last shot and it's 21 w/i 3.7%)
Average FPS - 833
Average FPE - 15.87
And at 10m here is the target with all 24 shots. (the bottom Diamond) I think my gun likes the AA pellets. And the best part? 7 pumps to charge hose and 24 more pumps to fill back to 3K. Efficiency is just about 1.4FPE/CUIN (according to the Sikes Calc)
(http://www.gatewaytoairguns.org/GTA/index.php?action=dlattach;topic=83494.0;attach=99735;image)
And I have a Hill Depinger in my tube so you will probably get at least 1 more shot, but I think the difference the depinger made is worth 1 shot.
By comparison the center diamond is 20 shots with my Daisy 901 at 10m
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Folks,
Anyone know the specs of the stock spring in the 1720T?
Stock is 1.75" long, .3" OD, has 14.5 coils, wire is ~.032 by measurement. Have no clue on Rate (lbs/in), Max Deflection (in) or Max Load (Lbs).
Also when they talk about a #7, #10, #12 spring are they talking about the Max Load or the Rate?
Any clue or help would be appreciated.
M
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Folks,
Anyone know the specs of the stock spring in the 1720T?
Stock is 1.75" long, .3" OD, has 14.5 coils, wire is ~.032 by measurement. Have no clue on Rate (lbs/in), Max Deflection (in) or Max Load (Lbs).
Also when they talk about a #7, #10, #12 spring are they talking about the Max Load or the Rate?
Any clue or help would be appreciated.
M
According to the Century Spring Catalog one of their springs with those dimensions (other manufacturers should be equal or real close) will have the following specs:
Music Wire - Max load - 6.1lb , Rate - 6.0lb/in, Max Def - 1"
Stainless - Max load - 4.1lb, Rate - 5.1lb/in, Max Def - .8"
When guys talk 7 or 10lb I'm pretty sure they are meaning Max load.
Middle of page "73". ( Is page 62 when the PDF opens on my computer)
http://www.centuryspring.com/pdfs/12-228compression.pdf (http://www.centuryspring.com/pdfs/12-228compression.pdf)
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Hi Rob,
Yea I was figuring stock was #6 very similar to the MROD larger springs. I am thinking of ordering a set of springs from Century that are the same length of 1.75" and have max load from 7.5 to 12 lbs. Not sure if the wire diameter matters so I was going to get SS and Steel springs. SS springs have a lower max load. I once fine tuned a MROD and the best spring was about 10-11 lbs.
From my guessiment I am figuring 1.75" x .3" x .038 (Century 70902) or 1.75" x .3" x.04" (century 70921).
The 1.5" spring does not seem to work well with the 1720T bolt.
Thanks !!
M
PS - Gun is louder than before. Just curious, do they make a longer shroud with more baffles that can help quiet it down some?
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Hi Rob,
Yea I was figuring stock was #6 very similar to the MROD larger springs. I am thinking of ordering a set of springs from Century that are the same length of 1.75" and have max load from 7.5 to 12 lbs. Not sure if the wire diameter matters so I was going to get SS and Steel springs. SS springs have a lower max load. I once fine tuned a MROD and the best spring was about 10-11 lbs.
From my guessiment I am figuring 1.75" x .3" x .038 (Century 70902) or 1.75" x .3" x.04" (century 70921).
The 1.5" spring does not seem to work well with the 1720T bolt.
Thanks !!
M
PS - Gun is louder than before. Just curious, do they make a longer shroud with more baffles that can help quiet it down some?
Spring works pretty good with mine. Are you having problems cocking? Mine is smooth cocking.
I bought mine used and it has a little 4" extension on it. I think it maybe have come from Marmot Militia. I think this is it here:
http://www.marmotmilitia.com/pistol-marauder-p-rod.html (http://www.marmotmilitia.com/pistol-marauder-p-rod.html)
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The refurb 1720T I got, did have 1.75" spring. It is near identical to the disco spring, if not same. The original prod one was 1.5", but I hear from some people that has been coming in 1.75" too. I haven't had any issue using 1.5", but doesn't hurt to try a slightly longer one, as long as it does not bind.
If you take spring length minus compressed length, times spring rate, equals max load. Max load is what most people advertise for airgun springs. You can measure your compressed length by pulling back the bolt and measuring where it contacts the spring, and then the distance at where it is fully cocked. That difference times rate is the load you are set at.
MM shroud ext does help, but if you want more quiet at these power levels, look at Hill, TKO, or Clauge LDCs. If you don't mind some DIY work, here is what I did: http://www.marauderairrifle.com/forum/viewtopic.php?f=33&t=10961 (http://www.marauderairrifle.com/forum/viewtopic.php?f=33&t=10961) I just sold both of my MM exts.
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Thanks John,
Thinking I don't want to remove the extension or LDC to fill the AG.
M
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You don't have to remove the extension to fill the gun. I have 1 on my .25 m-rod and the 1720T. It will put the noise level back to what it was before the mods.
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Thanks John,
Thinking I don't want to remove the extension or LDC to fill the AG.
M
Yea, that would be a PITA. I haven't had to do that though with MM ext, or Hill, or my DIY one.
PS: I have a piece of black electrical tape around the fill hose foster collar to prevent from scratching shroud.
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Ahhh... I went back where I had read this and it applied to the Clague with a shorter neck. This begs the question of how much longer do they add to the AG? Also does drilling the barrel end spacer holes out some help sound or performance?
I hope to fine tune the 1720T. I am wanting to flatten the curve out some more. Trying to find the 1.75" x .30" x .041 spring that is about 10-11 lbs max load. Century I found out has a minimum order so searching around.
Thanks,
M
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The Hill adds 5.75" inches which is still not bad for carbine. My DIY is slightly shorter. The MM ext adds 3.3"
Don't bother looking in McMasterCarr for the 1.75" springs.
BTW, I think you can shim the 1.5" springs a little. Find some brass washers that fit in hammer recess and allow the throw Allen wrench to pass thru.
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Well looking around Century has the best selection of springs. If my guessiments are close the stock spring is 6 lb. Not sure exactly what the 1.5" spring John sent me (in gun) is, but the 1.5" spring that Rob sent me is ~ 16 lb I think.
Here what 1.75" x .30" springs I plan to order:
7.5, 9.6, 11, 13, 16 lb
If you guys need any I can order you some since you have to order $40 worth. Just PM me.
Trial and error has put me on the .110 port, which is the largest without modifying the valve. Even if I modify valve I think anymore will bring my shot count down too much. I want 20-25 shots.
Did anyone modify the barrel end spacer?
M
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On a Prod, I have tried two small holes is the shroud, just ahead of the breech mount, with and without magic sponge, with no detectable diff in sound.
If you mean the airstipper, I drilled those out to 0.160". Not sure how much that helps, but do it as matter of course. You can go a little larger than that if you want, too.
The spring I sent you:
302 Stainless Steel Precision Compression Spring
1.5" Length, .3" OD, .042" Wire
Length 1.500"
Spring OD 0.30"
Wire Diameter 0.042"
Compressed Length 0.673"
Load 9.91 lbs.
Rate 17.38 lbs./inch
Additional Specifications Type 302 Stainless Steel—Meet ASTM A313.
RoHS Compliant
I would be interested in a sampling of springs. I'll PM latter.
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Thanks for the info. I went and took it out to check. My estimate was wrong because I thought it was a steel spring not a a SS spring. Is there some reason to use SS spring? From what I read Steel springs are more consistent and don't loose compression over time when compressed.
M
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Is there some reason to use SS spring?
No not really. MC has music wire precision springs, too.
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Well looking around Century has the best selection of springs. If my guessiments are close the stock spring is 6 lb. Not sure exactly what the 1.5" spring John sent me (in gun) is, but the 1.5" spring that Rob sent me is ~ 16 lb I think.
Here what 1.75" x .30" springs I plan to order:
7.5, 9.6, 11, 13, 16 lb
If you guys need any I can order you some since you have to order $40 worth. Just PM me.
Trial and error has put me on the .110 port, which is the largest without modifying the valve. Even if I modify valve I think anymore will bring my shot count down too much. I want 20-25 shots.
Did anyone modify the barrel end spacer?
M
The spring I sent is 11.4lb. (max load) I found a link to it.
Material: High Carbon Steel Music Wire
http://www.zoro.com/i/G2170594/ (http://www.zoro.com/i/G2170594/)
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According what I have read Music Wire (Steel ASTM A228) springs are the best for fatigue applications. SS springs are mainly for corrosive environments or higher temps (> 250 f). Other parts of this puzzle are the stock spring is left handed and the 1.5 springs you guys sent me are right handed. Doesn't seem like it matters...
M
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The spring I sent is 11.4lb. (max load) I found a link to it.
Material: High Carbon Steel Music Wire
http://www.zoro.com/i/G2170594/ (http://www.zoro.com/i/G2170594/)
Good info thanks Rob !! The zink coating made it slightly larger I guess.
So 9.91 lbs & 11.4 lbs at 1.5". So I am going to order 9.6, 11 & 13 lb 1.75" inch springs.
Thanks guys,
M
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I found a pack of 10 SS compression springs. 1.75" x .3" x .042" 9.84 lb for $13 shipped. They are RH coil but shouldn't matter. Also free returns offered.
This seems like a good SS spring. If they work well I will share...
Mike
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I found a pack of 10 SS compression springs. 1.75" x .3" x .042" 9.84 lb for $13 shipped. They are RH coil but shouldn't matter. Also free returns offered.
This seems like a good SS spring. If they work well I will share...
Mike
Wouldn't mind trying one if it helps flatten the curve.
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It only gets better... Google to the Rescue !!
Packs of 10 springs in 1.75" x .30" in 8, 9, 10, 11 lb on the way in. All returnable $13 shipped a pack
Enough to share if they work well. This should help the bolt cocking issue I was having with the 1.5" springs.
Will report back with results.
M
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This should help the bolt cocking issue I was having with the 1.5" springs.
Will report back with results.
M
What issue were you having?
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This should help the bolt cocking issue I was having with the 1.5" springs.
Will report back with results.
M
What issue were you having?
Yea, what issue? Can't think of any issue that the longer spring is going to help fix. I thought you were just trying other configs.
If binding, there are a couple of other things to check.
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The bolt was not always engaging with 1.5" springs. Put original back in and no issues...
M
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The bolt was not always engaging with 1.5" springs. Put original back in and no issues...
M
Spring engages sometimes, and not others??? or sear did not latch?
I have 1.5" springs in both of my 1720T and they always engage and latch.
Just checked: Both Prod and 1720T share the same spring part number: 1700-009
I suspect something else is causing issue.
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Ok trying to put my arms around this oring tune. John suggested I try 3 orings and 2 washer spacers. Tune seemed to want ~3/4 of a turn on striker. I took out the spacers yesterday leaving just the 3 orings and the striker seemed best a 0 turns. Zero turns actually gave me a more FPS with same shot number between 3000 - 2200 psi. Confused as always...
The new 1.75" hammer springs land tomorrow. 7.16, 8.21, 9.84, 11.88 lb. They are 10 pack each so I will have more springs than I need. Maybe I should offer a 4 pack assortment in the classified thread and try to recoup some of my $60. They fit 1720T, 1701P and BP2220 pistols. Or maybe change just my name to Mr. Spring!! ;D
Anyway look forward to a bunch of experimenting !!
M
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Yes, with three oring you will get more power, but you don't have the ability to turn it down from there. The two 0.035" SS washers and three orings was for the 15fpe and have some adjustment to lower it.
If you are right at the perfect tune for you. leave it there. With the throw screw full CCW you don't have to worry about creep. Many add a set-screw to the hammer to prevent creep of the throw screw.
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Mornin' John. Not sure what is meant by "turn it down". Seems like the same thing if you move the striker and the buffer out. I guess I need to study up some more on the buffer.
Thanks,
M
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Mornin' John. Not sure what is meant by "turn it down". Seems like the same thing if you move the striker and the buffer out. I guess I need to study up some more on the buffer.
Thanks,
M
I can answer that. In your top pic the gun velocity cannot be lowered anymore as the striker is all the out. In the bottom pic you can turn the striker further out, hence "turning it down". (in velocity)
In theory (and likely in practice) both pics as drawn will shoot the same velocity.
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Hi Rob, I can see that you can "Tune it down" more. Why not use 4 orings and turn the striker out some more. Seems like the orings are acting as a anti bounce device also. Why use 1/2 thickness washers as John recommends?
If this AG had a regulator seems like you could get a almost flat 825 fps tune for 25 shots which would be ideal.
I am wondering exactly what effect the port size, hammer spring load have on obtaining my goal of a 25 shot 825 fps string with 10.65gr pellets. So many variables finding the best port size and spring load. Add adjusting the striker & hammer spring makes it seem like infinite possibilities. Good thing I am retired, but I better order more pellets...
My guess is that my 1720T will do best with port of .095 and the 9.84 lb spring, 0 striker and 7 hammer spring with 3 orings.
Be safe,
M
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As John mentioned you ideally want the Striker set at zero to avoid any possibility of it moving. (I have a homemade "t" allen wrench made so that I know it is staying in the exact spot each time I take the gun out.)
Not sure on the regulator as it would take up some of the tube volume which is already only like 63CC's.
Nobody said it was going to be easy. I think sometimes we get lucky on a tune and hit it just right, if not it can be really hard due to all of the variables. And even harder, IMHO, due to the small volume of the tube.
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I was considering a regulator but after watching this video (https://www.youtube.com/watch?v=yHTxagAXR1k) I can see that they would be better with a bottle type AG, because as you say, the gun has such a small tube.
I know you and John have been experimenting with the 1720T a bunch. Would love to hear where your guys guess is for port size and hammer spring load rating to achieve my goal. From the factory I was getting a good shot string (>35 shots) but it was only low 600s fps.
M
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Would love to hear where your guys guess is for port size and hammer spring load rating to achieve my goal. From the factory I was getting a good shot string (>35 shots) but it was only low 600s fps.
M
I don't think you are going to get to 25 shots at 825.
With the .109 and the spring I sent you I am at 833 avg for 21 shots. I think without the depinger I would add 1 shot. If I took maybe an 1/8 turn off the HS I could add another for 23 total. Don't think 25 is possible.
I calculated my efficiency at 1.4 but it is probably higher as I do not know the volume of the depinger. Don't think it can get much better without some very very fine tuning.
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Rob,
Did you try any other port size than .109? If you did, how much did FPS fall off?
I got the 9.84 lb springs in. From that I have discovered why you guys went to 1.5" springs. More lbs equates to more coils. Well the my 1.75" spring will not cock with HS more than 5.5 turns. I checked the range and the adjustment unscrews at 6.5 turns. Not sure this matters but will find out when it stops raining.
Will report back later this week with findings.
M
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You can use 4 orings instead of 3 orings and two washers. It just means that the throw adjustment will be have more turns. About one additional turn, in this case. On a BSB, the throw adjustment is the velocity adjustment. The farther you turn the throw in for velocity, you also decrease your throw. I like to have as much throw as I can.
As far as regulators in Prod/1720T, search for some posts by Scott (motorhead). He did some extensive testing with a Milo regulator. At these power levels I doubt you will get any more shot count, given the loss of air volume for regulator and plenum needed for this power level.
Rob and I both had similar tunes of about 15FPE @ twenty something shots. Keep in mind we are using the slightly lighter jsbs than your h&n's. Your fps should be somewhere slightly lower or slightly lower shot count.
PS: The good thing about springs that are too long is, you can make them shorter. ;)
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Rob,
Did you try any other port size than .109? If you did, how much did FPS fall off?
No I didn't. Based on all of the stuff I found on several different articles/posts .109 seemed best so that's where I started, and then left it.
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Did you guys check the port size of the valve itself? The transfer port that John sent me is larger that the port in the valve. I drilled my extra transfer port at the same size as valve that I will try. It does not seem like a port larger than the port size in the valve would work any better than a port of the same size. Did you guys drill the valve port also?
M
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Did you guys drill the valve port also?
M
I did not drill mine. Didn't even take it out when I first did the mod
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I have drilled them out for other applications, but I thought the valve exhaust was the 0.110". If the tp was slightly larger, should not hurt, and might help if the barrel tp is slightly mis-aligned with the valve port.
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Went to shop and got some good measuring equipment. My stock valve port is exactly .109 which is 375 ten thousandths less than 7/64" drill. My stock breech port is .130. The transfer port John sent is .126. I drilled my extra red transfer port to exactly 7/64" which is .109375. This should be ideal. So far the only 1.75 springs that allow full travel are 7.16, 8.21 lb. 9.84 SS springs you lose ~ 3/4 - 1 turn on the Hammer Spring (HS) adjustment. The back ordered 9.04 lb spring should be here Monday. Looks like solid length of 1.75 springs have to be < .985" in order for AG to cock properly and allow full HS adjustment. Any 1.75 springs in SS seem to be too "fat" and don't allow gun to cock properly on full Hammer Spring adjustment. Will report back with shot data in a few days.
Take care,
Thanks Guys,
M
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Well I shot a tin and a half today trying different configurations. Results were disappointing. But got to love PCP so easy to shoot reload.
Results:
Both the 7.16 lb & 8.21 lbs 1.75" were just to light. Lots of shoots but nothing over 790 fps.
The 9.84 lb 1.75" spring shots were over 850 fps but could not adjust toward sweet spot because HS had such little adjustment. 11.88 1.75" spring had literally no adjustment but fired 11 shots over 900 fps. Will try 9.04 lb 1.75" spring when they arrive on Monday.
The best tune has been John's 9.91 lb 1.5" spring which string was in my 3rd post. Rob's 11.4 lb I was able to squeak out a respectable 14 shots 877.8 - 897.1 fps.
I played with the striker adjustment from 0 to 3 turns. Still puzzled what changes except less Fps. I could not see the string flatten out or peak differently.
M
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Not sure what happened to the tp. Maybe I drilled one, but sent another by mistake? I don't think it is going to impact your tune much. Go back to where you were and make very small adjustments in throw, like 1/8 T.
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Thanks John. You are right about small adjustments.
When tuning, in general terms, what flattens out the string? AG seems to start low and peek at 2500 or so. This AG would be the cat's meow with a regulator. I am guessing that is why they go to double tubes.
Thanks,
M
PS - Found this document which has helped me mucho. https://docs.google.com/document/d/1wsnI6_GJHqhD13YGlihlBpQzb_X91qmCsdCxT4iQtMA/edit (https://docs.google.com/document/d/1wsnI6_GJHqhD13YGlihlBpQzb_X91qmCsdCxT4iQtMA/edit)
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FWIW: If you go double tube, you can't use a reg. The air inlet from the 2nd tube is right where the reg has to be.
When close, I lower the throw very slightly, and sometime increase hammer preload. and the opposite. Going with a higher fpe usually has the consequences oh having higher Es.
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New spring 1.75" 9.1 lb. Best string - Hammer 0 HS 5.25 3000 - 2000 psi 10.65 gr No BSB
788.0
790.8
801.8
807.9
812.2
819.7
823.4
835.5
836.1
845.8
848.8
850.6
854.8
853.8
855.4
851.6
847.9
844.8
837.7
832.4
825.6
822.2
816.3
806.7
798.1
774.6
Everytime I use the BSB I get more peak and less shots. If I go to HS 6 no orings I get flatter curve with ~20 shots. I have to order more pellets. Shot over 800 in the last week.
This is how I tuned with orings. load 2500 psi, turned striker out to I hit my goal FPS. Played with HS. Tried 3, 3.5 & 4 orings. Gun is much quieter until I get to 2500 psi.
I feel like a I have failed. Set my goal too high. Need more air. When I set my HS at 6.5 I get 13 shots 842.7 - 880.3 fps. This would be good for hunting with spare air tank to refill often.
Will continue when I get some more pellets.
M
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Try a lower goal for your peak. Say 800-810fps with those 10.65g.
PS: I have been busy on some mods and fixes to the Prod rifle in Blaster clothing. Fixed a very slow leak, changed shroud, and free-floated the airtube. I have a few parts coming to finish this off. I will get back to some tuning with 1720T and brothers Prod. I have a WAR anti-bounce hammer coming to try as well.
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John,
Why do you need a anti bounce with a ring tune?
I also have come up with an interesting tuning tweak on the BSB. I put a digital caliper in the slot between the hammer and the end of tube slot. I increase the striker until the caliper shows some decrease from striker touching piston valve. With 3 orings that is about .35 of a turn. When I have tested the FPS this has always been the sweet spot, no matter what the HS adjustment. If I could just figure out the hammer spring adjustment this easy, it would become a AUTOMATIC tune. ;D
Got pellets in yesterday, going to shoot a few hundred or so today. I will let you know if I get any good strings.
M
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Why do you need a anti bounce with a ring tune?
I want to see how it compares to the BSB. I don't plan to try both together.
I have heard how quiet it has made some Mrods, and picked up one of the Prod blems that were for sale.
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Well going to leave the 1720T at this tune. 3100-2000 PSI, Striker .4, HS 6.25. Three orings and one washer. 9.04 LB 1.75 spring.
798.9
808.6
814.3
817.5
822.2
828.7
835.2
840.7
835.3
844.9
841.7
852.2
852.9
851.3
856.8
848.0
844.6
843.3
839.1
836.2
837.1
828.0
824.5
820.7
824.5
816.3
809.9
805.3
796.3
This is the best I have done. with the 1720T.
Thanks to all.
M